I assume dog engagement included straight cut gears. For $4900, it should.
The fact that the ratios are changed is a dead giveaway that the gears are replaced. Could you even have dog engagement with helically cut gears?
Edit: just saw your edit.

I don't know any specifics about this set, but I'm going to assume that the straight cut PPG gears are stronger than the stockers. They are really nice gears from the reviews I've read.